[lttng-dev] [PATCH lttng-ust] Implement LTTNG_UST_BLOCKING_RETRY_TIMEOUT

[Jonathan Rajotte Julien]

On 2016-11-04 10:25 AM, Philippe Proulx wrote:
> On Fri, Nov 4, 2016 at 10:23 AM, Jonathan Rajotte Julien
> <Jonathan.rajotte-julien at efficios.com> wrote:
>>
>> On 2016-11-04 10:22 AM, Philippe Proulx wrote:
>>> On Fri, Nov 4, 2016 at 10:13 AM, Jonathan Rajotte Julien
>>> <Jonathan.rajotte-julien at efficios.com> wrote:
>>>> Nitpicking:
>>>>
>>>> Should this be RETRY_DELAY_MS since other name scheme use the *_MS suffix
>>>> ?
>>>>
>>>> e.g:
>>>> LTTNG_UST_RING_BUFFER_RETRY_DELAY_MS
>>>> CONFIG_LTTNG_UST_DEFAULT_BLOCKING_RETRY_TIMEOUT_MS
>>>> timeout_left_ms
>>> Counterexample: LTTNG_UST_REGISTER_TIMEOUT.
>>>
>>> Phil
>>
>> Well we have a problem.
> Why? AFAIK the LTTng env. variables have no _MS suffix.

Was simply kidding regarding inconsistency. Which is not the end of the 
world.

Note that this is a #define ... not an env. variable and the define just 
before has the _MS suffix ...

Thanks
>
> See <http://lttng.org/man/8/lttng-sessiond/v2.8/#doc-_environment_variables>
> and <http://lttng.org/man/8/lttng-relayd/v2.8/#doc-_environment_variables>.
>
> Phil
>
>> Jonathan
>>
>>>>>       /*
>>>>>      * Non-static to ensure the compiler does not optimize away the xor.
>>>>> @@ -149,6 +150,14 @@ static struct timer_signal_data timer_signal = {
>>>>>           .lock = PTHREAD_MUTEX_INITIALIZER,
>>>>>     };
>>>>>     +int lttng_ust_blocking_retry_timeout =
>>>>> +               CONFIG_LTTNG_UST_DEFAULT_BLOCKING_RETRY_TIMEOUT_MS;
>>>>> +
>>>>> +void lttng_ust_ringbuffer_set_retry_timeout(int timeout)
>>>>> +{
>>>>> +       lttng_ust_blocking_retry_timeout = timeout;
>>>>> +}
>>>>> +
>>>>>     /**
>>>>>      * lib_ring_buffer_reset - Reset ring buffer to initial values.
>>>>>      * @buf: Ring buffer.
>>>>> @@ -1985,6 +1994,23 @@ void lib_ring_buffer_switch_slow(struct
>>>>> lttng_ust_lib_ring_buffer *buf, enum swi
>>>>>           lib_ring_buffer_switch_old_end(buf, chan, &offsets, tsc,
>>>>> handle);
>>>>>     }
>>>>>     +static
>>>>> +bool handle_blocking_retry(int *timeout_left_ms)
>>>>> +{
>>>>> +       int timeout = *timeout_left_ms, delay;
>>>>> +
>>>>> +       if (caa_likely(!timeout))
>>>>> +               return false;   /* Do not retry, discard event. */
>>>>> +       if (timeout < 0)        /* Wait forever. */
>>>>> +               delay = RETRY_DELAY;
>>>>> +       else
>>>>> +               delay = min_t(int, timeout, RETRY_DELAY);
>>>>> +       (void) poll(NULL, 0, delay);
>>>>> +       if (timeout > 0)
>>>>> +               *timeout_left_ms -= delay;
>>>>> +       return true;    /* Retry. */
>>>>> +}
>>>>> +
>>>>>     /*
>>>>>      * Returns :
>>>>>      * 0 if ok
>>>>> @@ -2001,6 +2027,7 @@ int lib_ring_buffer_try_reserve_slow(struct
>>>>> lttng_ust_lib_ring_buffer *buf,
>>>>>           const struct lttng_ust_lib_ring_buffer_config *config =
>>>>> &chan->backend.config;
>>>>>           struct lttng_ust_shm_handle *handle = ctx->handle;
>>>>>           unsigned long reserve_commit_diff, offset_cmp;
>>>>> +       int timeout_left_ms = lttng_ust_blocking_retry_timeout;
>>>>>       retry:
>>>>>           offsets->begin = offset_cmp = v_read(config, &buf->offset);
>>>>> @@ -2083,6 +2110,9 @@ retry:
>>>>>                                   >= chan->backend.buf_size)) {
>>>>>                                   unsigned long nr_lost;
>>>>>     +                             if
>>>>> (handle_blocking_retry(&timeout_left_ms))
>>>>> +                                       goto retry;
>>>>> +
>>>>>                                   /*
>>>>>                                    * We do not overwrite non consumed
>>>>> buffers
>>>>>                                    * and we are full : record is lost.
>>>>
>>>> --
>>>> Jonathan R. Julien
>>>> Efficios
>>>>
>>>>
>>>> _______________________________________________
>>>> lttng-dev mailing list
>>>> lttng-dev at lists.lttng.org
>>>> https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
>>
>> --
>> Jonathan R. Julien
>> Efficios
>>

-- 
Jonathan R. Julien
Efficios